1. Field Of The Invention
The invention comprises a new process for the production of 3-aminocrotononitrile by the dimerization of acetonitrile.
2. Background Art
3-Aminocrotononitrile is an intermediate product with a very wide spectrum of use. Thus, it is used, e.g., for the production of pharmaceutical agents (Chemical Abstracts, 85, 177262), the production of pesticides (Chemical Abstracts, 79, 53185b) and the production of azo dyes (Chemical Abstracts, 80, 122383).
Numerous processes are known for producing 3-aminocrotononitrile by the dimerization of acetonitrile in the presence of strong bases. But it is problematic in this reaction that acetonitrile with a base, such as, an amide ion, can react in various ways. Namely, if the nitrile group is attacked, the undesirable acetamidine is formed with the amide ion. Only the deprotonation of the acetonitrile to carbanion forms the prerequisite for the production of the desired 3-aminocrotononitrile.
Thus, according to Takeda et al., J. Pharm. Chem. Soc., Japan, 75, (1955), pages 957 to 959, a mixture of 3-aminocrotononitrile and acetamidine resulted after the reaction of acetonitrile with sodium amide at 100.degree. C. for 3 hours.
Subsequently, an attempt was made to foster the carbanion formation by specific performance of the reaction, i.e., by the use of sterically-demanding, strong bases.
Building upon the studies of Ziegler et al., Justus Liebigs Annalen, 504, (1933), 115, in which acetonitrile with lithium diethylamide as a base was reacted specifically to 3-aminocrotononitrile (iminonitrile) with 86 percent yield, Krueger, J. Organonmetal. Chem., 9, (1967), pages 125 to 134, synthesized 3-aminocrotononitrile with sodium-bistrimethylsilylamide in 90 percent yield. Except for the very good yields, the above-mentioned syntheses have the drawback that the sterically-demanding bases had to be produced--in part--in a complicated and particularly expensive manner, which constitutes an obstacle to the application of these processes in large-scale operations for economic reasons. (Separate comparison examples below make this clear.)
But it is also known from Swiss Patent No. 415,603 (and U.S. Pat. No. 3,290,355) to condense acetonitrile to 3-aminocrotononitrile with the help of sodium in an aliphatic hydrocarbon as the solvent at 70.degree. to 180.degree. C. in a yield of 90 percent. This dimerization has the drawback that, because of the reaction mechanism, 3 moles of acetonitrile relative to 2 moles of sodium have to be used instead of 2 moles of acetonitrile relative to 1 mol of sodium or a base. Even though this process constitutes an operating method, it is uneconomical for such reasons and is also unecological because of the accumulation of sodium cyanide.